A technique was developed for the purpose of studying the kinetics of metal reactions with water vapor at low partial pressures of H/sub 2/O(g). The details of the method were worked out in the study of the reaction of sodium and water vapor and adapted to work involving zirconium and aluminum alloys. Sodiurn investigations were made at 200 to 350 deg C and water vapor concentrations up to 400 ppm in a moving stresrn of helium carrier gas at a total pressure of one atmosphere. Studies involving zirconium and Zircaloy-2 were conducted at temperatures up to 1700 deg C and water vapor concentrations up to 30,000 ppm in one atmosphere He. The results of these experiments can be explained on the premise that the rate of reaction is controlled by the transport of water vapor through the helium. Good agreement was obtained between experimental results and calculations employing mass transfer considerations. A short stady of aluminum was made at 900 to 1400 deg C with water vapor concentrations up to 6400 ppm. It was concluded from the essentially quantitative reduction of water vapor and the appearance of powdered oxide in the system that a vapor phase reaction between aluminum and water vapor occurred. (auth).